bcache: configure the asynchronous registertion to be experimental

In order to avoid the experimental async registration interface to
be treated as new kernel ABI for common users, this patch makes it
as an experimental kernel configure BCACHE_ASYNC_REGISTRAION.

This interface is for extreme large cached data situation, to make sure
the bcache device can always created without the udev timeout issue. For
normal users the async or sync registration does not make difference.

In future when we decide to use the asynchronous registration as default
behavior, this experimental interface may be removed.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
index 6dfa653..bf7dd96 100644 (file)
--- a/drivers/md/bcache/Kconfig
+++ b/drivers/md/bcache/Kconfig
@@ -26,3 +26,12 @@ config BCACHE_CLOSURES_DEBUG
        Keeps all active closures in a linked list and provides a debugfs
        interface to list them, which makes it possible to see asynchronous
        operations that get stuck.
+
+config BCACHE_ASYNC_REGISTRAION
+       bool "Asynchronous device registration (EXPERIMENTAL)"
+       depends on BCACHE
+       help
+       Add a sysfs file /sys/fs/bcache/register_async. Writing registering
+       device path into this file will returns immediately and the real
+       registration work is handled in kernel work queue in asynchronous
+       way.

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index b971d8e..f9975c2 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2765,7 +2765,9 @@ static int __init bcache_init(void)
        static const struct attribute *files[] = {
                &ksysfs_register.attr,
                &ksysfs_register_quiet.attr,
+#ifdef CONFIG_BCACHE_ASYNC_REGISTRAION
                &ksysfs_register_async.attr,
+#endif
                &ksysfs_pendings_cleanup.attr,
                NULL
        };